1. Field of the Invention
The present invention is related to devices for adjusting the pressure of eyeglass temples against the head of a wearer to properly secure eyeglasses in position.
2. Description of the Prior Art
In the past, various types of spectacle frame adjusting devices have been constructed to vary the degree to which eyeglass temples press against the head of a wearer. The purpose of such devices is to prevent eyeglasses from sliding forward with the spectacle bridge working its way down the nose of the wearer. When this happens the wearer must push the spectacles back up into position every few minutes. This movement of the spectacles is both irritating and harmful to the wearer's eyesight, since the lens focus is altered when the eyeglasses slide forward. Prior temple bias adjusting devices have proven ineffective because the benefits of adjustable inward biasing of the bows have been nullified by the flexible nature of the eyeglass frames, or because prior devices have been overly complex and commercially unfeasible. As an example, U.S. Pat. No. 2,756,632 discloses a device in which a screw is directed angularly inward within each temple of an eyeglass frame to bear angularly against a surface in the frontal piece of the frame. However, the inward bias of the eyeglass bows from the pressure of the adjusting screw against an angular surface is distorted because of the play in the temple hinges and due to the deformation and slippage of the interacting bearing surfaces. Biasing the bows or temples of eyeglasses inward by virtue of pressure applied against a bearing surface at an angle considerably less than 90 degrees produces an inconsistent, pressure of the temples against the wearers head even after only very short periods of use. An alternative structure, with the same deficiences, is depicted in U.S. Pat. No. 3,874,775.
In general, conventional temple biasing mechanisms fail to provide the necessary degree of bias and rigidity because they act through far too short a lever arm. The forces induced on the wearers head are not uniform and change continuously even without adjustment while being worn. Because of the short lever arm of the application of the biasing force, any nonuniformities in temple alignment, wear, bending of the hinges and other minor variations are magnified greatly.